Current position > News detail
『Flanged Flow Meter Installation: Gasket and Bolt Torque Guidelines for Industrial Sensors』Related information(clamp on meter|electromagnetic meter|venturi meterrotameter|orifice meter|ultrasonic flow meter|mass flow meter|coriolis mass flow meter|coriolis flow meter|magnetic flow meter|magmeter flow meter|magflow flow meter|mag meter flow meter|electromagnetic flow meter|vortex flow meter|turbine flow meter|thermal mass flow meter|thermal flow meter|rotameter flow meter)
Flanged Flow Meter Installation: Gasket and Bolt Torque Guidelines for Industrial Sensors
Quick Answer: Most flanged flow meter leaks come from gasket mismatch and uneven bolt torque. Select the gasket material for your fluid, temperature, and flange pressure class. Tighten bolts in a cross pattern with a calibrated torque wrench. A DN50 PN16 flow meter with carbon steel M16 bolts typically needs 35 Nm final torque. Silver Instruments supplies flanged flow meters and industrial sensors with torque tables for water, chemical, gas, and food plants.
Flanged flow meters connect directly to pipe flanges. A bad installation will leak, offset the meter, or warp the liner. We have seen this on customer sites many times. Most engineers skip the torque table and gasket check. That shortcut costs downtime later.
Why Gasket Selection Decides Flanged Flow Meter Leakage
A gasket seals the space between the meter flange and the pipe flange. If the gasket inner diameter is too small, it blocks flow and creates a pressure drop. If the gasket is too soft, it crushes under bolt load and leaks after thermal cycling. EN 1092-1 PN16 flanges use a different gasket face than ASME B16.5 Class 150 flanges. Mixing these standards is a common mistake in plants in Southeast Asia and Latin America.
For most DN15 to DN80 flow meters on water or low pressure air, a 1.5 mm to 3 mm thick EPDM or PTFE sheet gasket works. A paint manufacturer in Thailand ordered a flanged electromagnetic flow meter for solvent batching but reused an EPDM gasket. The gasket swelled within two days. We replaced it with a PTFE gasket and the meter has run without leaks for over a year.
Which Gasket Materials Work for Industrial Flow Meters
Here is the thing. Gasket material is not a universal choice. Water and wastewater plants can use EPDM rubber gaskets from -20 °C to 120 °C. Chemical plants with acids, caustic, or solvents should use PTFE gaskets from -20 °C to 150 °C. Steam and high temperature oil lines need spiral wound gaskets with graphite or PTFE filler. Graphite works up to 450 °C and handles Class 300 and higher.
Silver Instruments recommends the gasket thickness match the flange raised face depth. A DN50 PN16 raised face flange has a typical depth of 2 mm. A 3 mm gasket crushes to fit but stores less energy. A 1 mm gasket may not fill surface roughness. Do not reuse old gaskets. A used gasket has already taken a compression set.
Bolt Torque Values for DN15 to DN200 Flanged Flow Meters
Torque values depend on bolt size, bolt material, gasket type, and pressure class. The values below apply to carbon steel bolts and PN16 or Class 150 flanges. Use a calibrated torque wrench. Do not use an impact gun for final passes.
DN15 PN16 M12 bolts need 15 Nm to 20 Nm final torque. DN25 PN16 M12 bolts need 20 Nm to 25 Nm. DN50 PN16 M16 bolts need 35 Nm to 40 Nm. DN80 PN16 M16 bolts need 45 Nm to 55 Nm. DN100 PN16 M16 bolts need 65 Nm to 75 Nm. DN150 PN16 M20 bolts need 110 Nm to 130 Nm. DN200 PN16 M20 bolts need 180 Nm to 220 Nm. For Class 300 flanges, multiply by 1.3 to 1.5. For stainless steel bolts, reduce torque by 10 to 15 percent. Lubricate the threads lightly with copper or molybdenum grease. Dry threads create false torque readings.
We have seen a customer in Vietnam torque a DN80 flow meter to 55 Nm on dry threads. It leaked at 6 bar water pressure. After cleaning and greasing the threads, the same torque held 10 bar without leaks.
Cross Tightening Pattern and Pass Sequence
Do not tighten bolts in a clockwise order. That warps the flange and the meter body. Use a star or cross pattern. Start with the bolt at the top of
_600x400.jpg)
Most flanged flow meter installations need three passes. First pass to 30 percent of final torque. Second pass to 60 percent. Third pass to 100 percent. After 24 hours, check the torque again. Gaskets relax after the first thermal cycle. In practice, this recheck catches most small leaks before they become a shutdown.
Installation Errors We See on Customer Sites
The most frequent error is a mismatched gasket inner diameter. A full face gasket on a raised face flange blocks the flow path. The meter then reads low or the pump trips on pressure. Another error is one side tightened fully before the other side has any load. This twists the meter body and can crack a ceramic liner. We have seen this on electromagnetic flow meters in water plants in Australia and Chile.
Because the flange face carries the seal load, flatness matters. If the pipe flanges are not parallel, the bolts pull the meter into alignment. That stresses the liner and the flange. Use a feeler gauge to check the gap between flange faces. The gap should not vary by more than 0.5 mm around the circle. For DN100 and larger, add pipe supports near the meter. Do not use the flow meter as a pipe support.
Which Silver Instruments Flow Meters Need Flanged Installation
Silver Instruments supplies flanged electromagnetic flow meters from DN15 to DN300 for water, wastewater, chemical, and food plants. Coriolis mass flow meters come with flanged connections from DN3 to DN150 for oil, gas, and batch dosing. Vortex flow meters cover DN25 to DN200 for steam and compressed air. Oval gear flow meters come with flanged ends from DN10 to DN100 for fuel and oil transfer.
Every flanged meter ships with a dimension drawing that shows bolt circle, gasket face, and torque sequence. If your site uses JIS 10K, ASME B16.5, or EN 1092-1, specify that on the inquiry. A desalination plant in Oman ordered a DN150 electromagnetic flow meter with EN 1092-1 PN16 flanges and EPDM gaskets. It passed hydrotest at 16 bar without pipe modification.
FAQ
Q: What happens if I overtighten flanged flow meter bolts?
A: You can crush the gasket, warp the flange, or crack the liner. On a DN50 PN16 meter, anything above 45 Nm on M16 carbon steel bolts is usually too high.
Q: Can I reuse a gasket for a flanged flow meter?
A: No. A used gasket has already compressed under bolt load and will not recover. Replace the gasket every time the meter is removed.
Q: What torque should I use for PTFE lined flow meters?
A: PTFE liners are more sensitive to crush. Use the lower end of the torque range for your flange size and gasket type. Do not exceed 40 Nm on DN50 PN16 flanges unless the drawing says otherwise.
Q: Which flange standard should I order for a flow meter in Southeast Asia?
A: Many plants in Southeast Asia use EN 1092-1 PN16 or JIS 10K flanges. But check the existing pipe flange standard. Silver Instruments can match EN, ASME, JIS, and DIN flange standards.
Q: How do I get a flanged flow meter quote from Silver Instruments?
A: Send us your pressure in bar, temperature in °C, pipe size in DN, and flow range. Include the fluid name, viscosity, and flange standard. Reach Silver Instruments at Tel: +86-25-68650347, WhatsApp: +86-25-52155837, WeChat: +86 15365082610.
For more technical details on flanged flow meter installation, visit flow-meter.com.au or contact our application engineers. We stock common DN sizes and gasket kits for same week shipment in many regions.